/**
 * Copyright (c) 2008, Piercarlo Slavazza
 * All rights reserved.
 *
 * Redistribution and use in source and binary forms, with or without
 * modification, are permitted provided that the following conditions are met:
 *     * Redistributions of source code must retain the above copyright
 *       notice, this list of conditions and the following disclaimer.
 *     * Redistributions in binary form must reproduce the above copyright
 *       notice, this list of conditions and the following disclaimer in the
 *       documentation and/or other materials provided with the distribution.
 *     * The name of Piercarlo Slavazza cannot be used to endorse or promote products
 *       derived from this software without specific prior written permission.
 *
 * THIS SOFTWARE IS PROVIDED BY Piercarlo Slavazza ''AS IS'' AND ANY
 * EXPRESS OR IMPLIED WARRANTIES, INCLUDING, BUT NOT LIMITED TO, THE IMPLIED
 * WARRANTIES OF MERCHANTABILITY AND FITNESS FOR A PARTICULAR PURPOSE ARE
 * DISCLAIMED. IN NO EVENT SHALL Piercarlo Slavazza BE LIABLE FOR ANY
 * DIRECT, INDIRECT, INCIDENTAL, SPECIAL, EXEMPLARY, OR CONSEQUENTIAL DAMAGES
 * (INCLUDING, BUT NOT LIMITED TO, PROCUREMENT OF SUBSTITUTE GOODS OR SERVICES;
 * LOSS OF USE, DATA, OR PROFITS; OR BUSINESS INTERRUPTION) HOWEVER CAUSED AND
 * ON ANY THEORY OF LIABILITY, WHETHER IN CONTRACT, STRICT LIABILITY, OR TORT
 * (INCLUDING NEGLIGENCE OR OTHERWISE) ARISING IN ANY WAY OUT OF THE USE OF THIS
 * SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF SUCH DAMAGE.
 */

package com.libapml;

import java.net.URI;

import org.apache.lucene.index.IndexReader;
import org.apache.lucene.index.TermFreqVector;
import org.apache.lucene.store.Directory;

import com.libapml.indexer.LuceneWriter;
import com.libapml.util.Helper;

public class LuceneReader {
	
	private Directory luceneDirectory;
	
	private LuceneReader(Directory luceneDirectory) {
		
		Helper.checkNotNull(luceneDirectory);
		
		this.luceneDirectory = luceneDirectory;
	}

	private ApmlIndex read() throws ApmlException {
		
		ApmlIndex index = new ApmlIndex();
		
		try {
			IndexReader reader = IndexReader.open(luceneDirectory);
			
			int docCount = reader.maxDoc();
			for (int i = 0; i < docCount; i++) {
				
				URI documentUri = new URI(reader.document(i).getFieldable(LuceneWriter.DOC_URI_FIELD).stringValue());
				LuceneDocument luceneDocument = new LuceneDocument(luceneDirectory, documentUri, index);
				
				TermFreqVector termsVect = reader.getTermFreqVector(i, "contents");
				int[] occurrencies = termsVect.getTermFrequencies();
				String[] terms = termsVect.getTerms();

				for (int j = 0; j < terms.length; j++) {
					
					if (occurrencies[j] > 2 && terms[j].length() > 2) {
						Concept concept = index.getConcept(terms[j]);
						if (concept == null) {
							concept = new Concept(terms[j]);
							index.addConcept(concept);
						}

						concept.add(new ConceptOccurrenceInDocument(
								concept,
								luceneDocument,
								occurrencies[j]));
					}
				}
				
			}
			
			index.close();
			
		} catch (Exception e) {
			throw new ApmlException(e);
		}
		
		return index;
	}

	public static ApmlIndex read(Directory luceneDirectory) throws ApmlException {
		
		return new LuceneReader(luceneDirectory).read();
		
	}
	
}
